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Humphry Davy (1778-1829), British chemist, testing his safety lamp in a mine. Several miners had been killed when their torches ignited pockets of methane in mines. The Davy lamp was designed in such a way that it was unable to do this, and thus its introduction in 1815 saved many lives. As well as this invention, Davy isolated the elements potassium, sodium, calcium, magnesium, barium and strontium, by passing an electric current through their compounds (electrolysis). He also discovered nitrous oxide, or laughing gas, the gas that was used as the first anaesthetic. (KEYSTONE/SCIENCE PHOTO LIBRARY/SHEILA TERRY)